(1) Field of the Invention
The present invention is concerned generally with the field of microelectromechanical system (MEMS). The present invention relates to a fixture for use in microsystems, in particular for the self-aligning mounting and fixture of microchannel plates, and to a device at least comprising a fixture according to the invention and a microchannel plate.
(2) Description of Related Art
Microsystems engineering combines methods from microelectronics, micromechanics, microfluidics and microoptics, but also developments in informatics, biotechnology and nanotechnology, by combining developments and structures from these fields to form new systems. The dimensions of the function-determining structures lie in the micrometers range, which can be used as delimitation with respect to nanotopology.
Whereas microelectronics is restricted to electrical components such as transistors (CPU) and capacitors (RAM), microsystems engineering is concerned with the design and production of microelectronic circuits and micromechanical and microoptical components and the integration thereof to form a system both as discrete components and monolithically e.g. in semiconductor materials such as crystalline silicon or gallium arsenide.
In microsystems, also called micro electro mechanical systems (MEMS), sensors, actuators and data processing cooperate. Examples are optical sensors in cableless mouses, or bubble jet print heads of modern printers, acceleration and rate-of-rotation sensors for triggering airbags and for controlling stability and navigation systems, instruments for minimally invasive surgery, endoscope systems, chemical sensors for foodstuff monitoring, micro hard disks or micromirror actuator chips in beamers or organic light-emitting diodes. An area on the periphery of microsystems engineering is microprocess technology, which is concerned with physical and/or chemical processes that proceed in microstructured apparatuses.
Microsystems were formerly based predominantly on semiconductor electronics; the base material (substrate) was generally silicon or gallium arsenide. Nowadays, microsystems can also be produced inexpensively from plastics and the results in the field of materials research are used for multifunctional systems.
Microsystems are often not produced monolithically from a wafer, but rather comprise different components that are connected to one another to form a hybrid microsystem. The microsystem accordingly has connection locations that permit the connection of a plurality of components to form a system. One example of such a connection location is fixtures for accommodating and fixing a component of the microsystem. A micro mass spectrometer will be considered as an example for illustration purposes.
Micro mass spectrometers are known from the prior art (see e.g. “Complex MEMS: A fully integrated TOF micro mass spectrometer” published in Sensors and Actuators A: Physical, 138 (1) (2007), 22-27). It has not been possible hitherto to produce all the components of a micro mass spectrometer monolithically in one workpiece. The secondary electron multiplier is e.g. a complex component which has to be fabricated separately and be connected to the remaining components of a micro mass spectrometer to form an overall system. This requires a fixture that accommodates the secondary ion multiplier and fixes it relative to other components of the system.
The use of a microchannel plate as a secondary ion multiplier is obvious in the case of a micro mass spectrometer.
A microchannel plate is a planar, image-resolving secondary electron multiplier. It serves for the low-noise amplification of small currents of free electrons or other ionizing particles which strike the input side of the plate with a certain energy and instigate secondary electrons there.
The microchannel plate comprises two metallized plate sides between which an acceleration voltage is present. The plate itself is composed of a semiconductor and is perforated in a manner similar to a sieve, or pervaded by microscopically fine channels typically having a hole spacing of approximately 10 μm and a diameter of approximately 6-8 μm. The plate has a thickness of a few tenths of a millimeter and the channels are tilted by approximately 10° relative to the plate axis, such that the incident electrons definitely impinge on the channel wall repeatedly. They are then accelerated by an electrical voltage present between the plates along the channels and are multiplied upon each wall impact. Each individual channel thus behaves like a microscopic electron multiplier such as is used in a photomultiplier, for example.
At the exit side, the number of electrons has increased by approximately 1000-fold as a result of multiple impacts with the channel wall. Through a post-acceleration section, the amplified (=multiplied) electrons are directed onto the actual detector, usually a luminescent screen, but also for example an ebCCD, i.e. electron bombarded CCD, a special form of the CCD for detecting free electrons, and also onto an electron trap, e.g. embodied as a Faraday detector.
Microchannel plates are used in various measuring systems such as mass spectrometers, electron multipliers and night vision systems for amplifying small “primary” electron or ion currents. If primary beams (electrons, ions, photons) occur on very small cross sections at precisely defined locations, as is applicable in particular in applications in microsystems engineering or integrated optics and microoptics, the channels of the microchannel plates have to be aligned with respect thereto with an accuracy in the micrometers range.
For such applications it would be advantageous if this microchannel plate integrated in hybrid fashion could be used in a guide oriented directly with respect to the primary beam structure.
In addition to the alignment with respect to the ion channel with micrometer accuracy, it would be advantageous for the holding device to simultaneously fix the microchannel plate at this location and make electrical contact with it. In the case of the example described, an electron trap is furthermore necessary and it must be ensured that electric fields resulting from the high voltage at the plate are shielded in such a way that they do not influence the function of the microsystem, e.g. that of a mass spectrometer.
The orientation of components is of great importance in the production of microoptical systems, too. The fundamental nature of light dictates that light-generating, -transmitting and -altering components have to be positioned precisely with respect to one another. Mounting devices and fixtures in microoptical are generally restricted to mechanical structures that predominantly serve for the precise positioning of the components. They preferably use structures which are introduced into silicon substrates and on which different components (e.g. optical fiber, laser and detector diodes) are integrated in a manner aligned with respect to one another, or metallic, preferably circular, structures composed of solder, so-called bumps, which permit alignment during the solder reflow process.
Connection by soldering and laser welding are two conventional securing and mounting techniques in microsystems engineering. In the case of laser welding, by way of example, the component to be secured can be held in a clamp, which is then oriented and welded to a substrate. What is disadvantageous is, inter alia, that the component is irreversibly connected to a substrate; it is not possible to exchange the component.
EP1230571B1 describes a device for active optical fiber orientation with a plastically deformable holding device, which, however, does not include any electrical contact-connection.
EP1345843B1 describes a device for securing totally released microcomponents, which, however, does not enable a component to be mounted in a self-aligning fashion.
Therefore, proceeding from the prior art described, the object formulated is that of providing a fixture for the integration of components in MEMS which enables the component to be mounted in a self-aligning fashion. The fixture sought is intended to enable a reversible connection between the component and a substrate. Electrical contact-connection is intended to be effected in addition to the mechanical fixing of the component. The fixture is intended to be cost-effective to produce and flexible and simple to handle.
Surprisingly, it has been found that this object can be achieved particularly effectively by means of conductive spring structures that are constructed on a non-conductive substrate.